Blade outer air seal system for controlled tip clearance

Abstract

A blade outer air seal system for a gas turbine engine includes a plurality of ring carriers made of a first material having a first coefficient of thermal expansion. A plurality of seal segments are carried, respectively, on the plurality of ring carriers. A ring member is carried in the plurality of ring carriers. The ring member is made of a second material that is different from the first material in composition. The second material has a second coefficient of thermal expansion such that the first coefficient of thermal expansion is 75-175% of the second coefficient of thermal expansion.

What is claimed is: 
     
       1. A blade outer air seal system for a gas turbine engine, comprising:
 a plurality of ring carriers made of a first material having a first coefficient of thermal expansion; 
 a plurality of seal segments carried, respectively, on the plurality of ring carriers; 
 a ring member carried in the plurality of ring carriers, the ring member being made of a second material having a second coefficient of thermal expansion such that the first coefficient of thermal expansion is 75-175% of the second coefficient of thermal expansion, wherein the first material and the second material are different metallic alloys, and the first coefficient of thermal expansion and the second coefficient of thermal expansion are both above 5 part per million per degree Celsius. 
 
     
     
       2. The blade outer air seal system as recited in  claim 1 , wherein the first coefficient of thermal expansion is less than 150% of the second coefficient of thermal expansion. 
     
     
       3. The blade outer air seal system as recited in  claim 1 , wherein the first coefficient of thermal expansion is 100-175% of the second coefficient of thermal expansion. 
     
     
       4. The blade outer air seal system as recited in  claim 1 , wherein the first coefficient of thermal expansion is 115-135% of the second coefficient of thermal expansion. 
     
     
       5. The blade outer air seal system as recited in  claim 1 , wherein the second material has a density and a heat capacity, and a product of the density and the heat capacity is 0.032 BTU/(in 3 *° R)±10% (1.145 MJ/m 3 *K). 
     
     
       6. The blade outer air seal system as recited in  claim 1 , wherein the plurality of ring carriers define an internal cavity, and the ring member is carried in the internal cavity. 
     
     
       7. The blade outer air seal system as recited in  claim 1 , wherein each of the plurality of ring carriers circumscribes a section of the ring member. 
     
     
       8. The blade outer air seal system as recited in  claim 1 , wherein the second material is an iron-based alloy. 
     
     
       9. The blade outer air seal system as recited in  claim 1 , wherein a plot of blade tip clearance versus engine power for the plurality of ring carriers and the ring member exhibits a lower incline in comparison to a plot of blade tip clearance versus engine power for a baseline metallic carrier and a baseline non-metallic ring. 
     
     
       10. A gas turbine engine comprising:
 a compressor section; 
 a combustor in fluid communication with the compressor section; and 
 a turbine section in fluid communication with the combustor, the turbine section having a blade outer air seal system including a plurality of ring carriers made of a first material having a first coefficient of thermal expansion, a plurality of seal segments carried on the plurality of ring carriers and a ring member carried in the plurality of ring carriers, the ring member being made of a second material that is different from the first material in composition, the second material having a second coefficient of thermal expansion such that the first coefficient of thermal expansion is 75-175% of the second coefficient of thermal expansion, wherein the first material and the second material are different metallic alloys, and the first coefficient of thermal expansion and the second coefficient of thermal expansion are both above 5 part per million per degree Celsius. 
 
     
     
       11. The gas turbine engine as recited in  claim 10 , wherein the first coefficient of thermal expansion is less than 150% of the second coefficient of thermal expansion. 
     
     
       12. The gas turbine engine as recited in  claim 10 , wherein the second material has a density and a heat capacity, and a product of the density and the heat capacity is 0.032 BTU/(in 3 *° R)±10% (1.145 MJ/m 3 *K). 
     
     
       13. The gas turbine engine as recited in  claim 10 , wherein the second material is an iron-based alloy. 
     
     
       14. The gas turbine engine as recited in  claim 10 , wherein a plot of blade tip clearance versus engine power for the plurality of ring carriers and the ring member exhibits a lower incline in comparison to a plot of blade tip clearance versus engine power for a baseline metallic carrier and a baseline non-metallic ring. 
     
     
       15. The gas turbine engine as recited in  claim 10 , further comprising a fan section coupled to be driven by the turbine section, the turbine section having a first turbine and a second turbine, the first turbine having a maximum rotor diameter and the fan section having a fan diameter such that a ratio of the maximum rotor diameter divided by the fan diameter is less than 0.6. 
     
     
       16. A method for controlling thermal response in a blade outer air seal system for a gas turbine engine, the method comprising:
 in a blade outer air seal system that includes a plurality of ring carriers made of a first material, a plurality of seal segments carried on the plurality of ring carriers and a ring member carried in the plurality of ring carriers and made of a second material that is different from the first material in composition, 
 establishing a thermal response rate of the control ring to be slower than a thermal response rate of the plurality of ring carriers with respect to a surrounding thermal environment by:
 (a) selecting a first coefficient of thermal expansion of the first material in coordination with selecting a second coefficient of thermal expansion the second material such that the first coefficient of thermal expansion is 75-175% of the second coefficient of thermal expansion, and 
 (b) providing the ring member within the plurality of ring carriers such that the plurality of ring carriers shields the ring member from the surrounding thermal environment, wherein the first material and the second material are different metallic alloys, and the first coefficient of thermal expansion and the second coefficient of thermal expansion are both above 5 part per million per degree Celsius. 
 
 
     
     
       17. The method as recited in  claim 16 , wherein the first coefficient of thermal expansion is less than 150% of the second coefficient of thermal expansion. 
     
     
       18. The method as recited in  claim 16 , wherein the second material has a density and a heat capacity, and a product of the density and the heat capacity is 0.032 BTU/(in 3 *° R)±10% (1.145 MJ/m 3 *K). 
     
     
       19. The method as recited in  claim 16 , wherein the second material is an iron-based alloy. 
     
     
       20. The method as recited in  claim 16 , wherein a plot of blade tip clearance versus engine power for the plurality of ring carriers and the ring member exhibits a lower incline in comparison to a plot of blade tip clearance versus engine power for a baseline metallic carrier and a baseline non-metallic ring.